If you can have more than 2 water and food points you can leave them all together without problems, if you don't the astralorps will stop the little ones eating and drinking, but they will sleep together fine. After 6 weeks old, chicks are fine down to freezing, as long as they is at least 4 of them.
This morning I put them outside in a big run I have just remodeled and made heaps bigger I had 3 food and 5 water containers and the australorps still picked on the littlies so they huddled in a corner. I went in and divided it up again. I am thinking of dividing the night time coop up better so they will not fight and the littlies will have more room than they have over the last few days. I read that a new area that didn't belong to anyone and heaps of feeders and water would help but it didn't, maybe mine are just nasty. they are not supposed nasty just bossy. Here's hoping when they get bigger and there's 6 babies and only 2 bigger ones they will hold there own or maybe I should just wait and see who's a rooster then worry about integrating, it might all be for nothing. I won't be able to keep roosters.